1. Field of the Invention
This invention relates to a load port used to transfer a wafer from and into a wafer accommodating vessel such as a FOUP (Front-Opening Unified Pod), a MAC (Multi Application Carrier) or a FOSB (Front Open Shipping Box) upon semiconductor manufacture.
2. Description of the Related Art
In a manufacturing process of semiconductors, a wafer is processed in a clean room in order to assure an enhanced yield and enhanced quality. However, in these days in which high integration of devices, miniaturization of circuits and increase in size of wafers have proceeded, it is difficult to manage fine dust in the inside of the overall clean room from a point of view of the cost and the technology. Therefore, as a method which replaces enhancement in cleanness of the inside of the overall clean room, a countermeasure is taken which adopts a “minienvironment system” which enhances the cleanness only in a local space around a wafer to carry out transportation and other processes of wafers. In the minienvironment system, in order to transport and accommodate a wafer in a highly clean environment, a wafer accommodating vessel for exclusive use is utilized. In order to transfer a wafer between a wafer accommodating vessel and a semiconductor manufacturing apparatus, an interface called a load port is utilized.
Particularly in recent years, increase in size of wafers has advanced, and recently, also formulation of peripheral apparatus for wafers of a diameter of 450 mm has been progressed. As wafer accommodating vessels, a FOUP, a MAC including an H-MAC (Horizontal-MAC), a FOSB and so forth are available. The wafer accommodating vessels listed above have a common structure in that they include a door provided for one of upright faces such that it can be opened and closed and can close up the wafer accommodating vessel. The door is opened and closed by a door opening and closing mechanism provided on a load port in a state in which the wafer accommodating vessel is placed on a vessel receiving table of the load port. When the door is in an open state, a wafer is carried into or out of the wafer accommodating vessel by a transport robot provided on an EFEM (Equipment Front End Module) on which the load port is provided.
The load port includes, as a mechanism for opening and closing a door of a wafer accommodating vessel (the door is hereinafter referred to as “vessel door”), a door member for holding the vessel door in a closely contacting state to open and close the vessel door. The mechanism of the load port further includes a post-like support member for supporting the door member, and a door opening and closing mechanism for moving the door member toward and away from the wafer accommodating vessel together with the support member and moving the door member upwardly and downwardly together with the support member. The door member is disposed such that it just fits with an aperture section formed in a frame section in the form of a plate of the load port which configures part of an outer wall of an EFEM. When the vessel door is to be placed into an open state, the door opening and closing mechanism is rendered operative to retract the door member, which holds the vessel door in a closely contacting state, and the support member away from the wafer accommodating vessel (toward the internal space of the EFEM) once and then downwardly. When the vessel door is to be placed into a closed state, the associated members operate in the reverse procedure.
On the other hand, the wafer accommodating vessel can accommodate a plurality of wafers in a plurality of stages disposed upwardly and downwardly relative to each other. However, in order to accommodate the wafers stably, a retainer capable of retaining a wafer in each of the stages by elastic force is provided on an inwardly directed face of the vessel door (refer to Japanese Patent Laid-Open No. 2008-135434). The retainer is configured in the following manner. In particular, it has elasticity and presses and retains a wafer in the wafer accommodating vessel from the inner face side of the vessel door while it is elastically deformed so that the wafer is positioned at its accommodated position and damage to the wafer, which is thin and fragile, can be prevented.